German No. 34 00 711 (corresponding to U.S. Pat. No. 4,638,782) describes an open-loop and/or closed-loop control of a final controlling element for influencing the metering of fuel into an internal combustion engine, wherein a system deviation is defined starting from a setpoint and an actual value. On the basis of the system deviation, a loop controller specifies a manipulated variable to be received by the final controlling element. A loop controller, preferably having Proportional-Plus-Integral (PI) action executes a closed-loop control at high rotational speeds. In certain operating states, particularly at low rotational speeds, only an open-loop control of the final controlling element takes place.
Such PI controllers require a very high degree of complexity for applications, especially when different parameter sets are provided for high-level and low-level signal action. At low rotational speeds, no closed-loop control operation is possible. Instead, only an open-loop control of the final controlling element is provided. Another disadvantage of the known procedure is that it is very difficult to optimally design a loop controller. For example, for large system deviations, it is desirable to have very large gains (i.e., amplification factors) in the loop controller. On the other hand, when there are small system deviations (low-level signal action), it is advantageous to have very small gains.